In order to assure that low loss optical fibers which are produced today are not diminished in their effectiveness in systems, the fibers are connected through intermateable connectors which preserve those low losses. Desirable is the use of a hermaphroditic connector in which each optical fiber may be terminated with such a connector and joined to another such connector without the need for any intervening device such as a coupling. One of the advantages of such a system is that it obviates the need to inventory couplings and avoids the possibility for misplacing same in the field. Further, the deployment in the field of cables each end of which is terminated with a hermaphroditic connector avoids the mistake of juxtaposing an end of a cable terminated with a non-hermaphroditic connector with an identical non-mateable terminated end of another cable.
Another desired property of an optical fiber connector is the avoidance of forces applied to the optical connection between two connectors. In at least one optical fiber cable of the prior art which is to be terminated with a plug, a core comprising at least one optical fiber is enclosed in a jacket, non-metallic filamentary strength members such as polymeric yarn, for example, and an outer jacket. It becomes important to prevent the transmittal of tensile forces to optical fibers at their terminations with the plugs. If this is not done, the fibers may be broken or microbending losses in the fiber may occur and degrade the quality of the transmission. Also, any forces which are not diverted to other portions of the connector may be imparted to a plug thereby disturbing its seating in a coupling sleeve and its critical alignment with the other plug.
In order to avoid such losses at a connection, provisions must be made for avoiding the application of forces to the optical fibers after portions of a sheath system of the cable have been removed for termination. Instead, any pulling forces must be transferred to a connector housing. When a connection is to be made, the strength members must be coupled to a housing portion of the connector so that forces are transferred to the housing before the forces reach the optical fiber terminations.
This requirement becomes even more important in special environments. For example, what is needed is an optical fiber connector assembly to withstand stringent environmental and mechanical requirements which are imposed on military as well as on commerical communications equipment. One requirement is that there is no attenuation increase at an operating tensile load of about 1700 Newtons. The transfer of forces from the cable to the connector housing instead of to the plugs must be made simply and through a termination of the strength members.
Available in the prior art is a hermaphroditic dual biconic optical fiber connector which is effective to terminate an optical fiber cable which includes two optical fibers and a non-metallic, filamentary strength system. Included in the connector are a housing having a longitudinal axis and force transfer means disposed adjacent to a cable entrance end of the housing and through which the optical fibers extend.
The force transfer means is effective to clamp the non-metallic strength system of the cable to transfer forces from the cable to the housing. Also, the force transfer means includes two conformable, substantially smooth conically shaped surfaces which are held in mating relationship with each other with portions of the strength member system therebetween. Each surface diverges in a direction from the cable entrance end of the housing toward another end such that an included angle between diametrically opposed lines on each of the surfaces which are disposed in a plane passing through the axis of revolution of each surface does not exceed a predetermined value.
Conically shaped plugs which terminate the optical fibers in the prior art hermaphroditic, dual biconic connector are disposed adjacent to the other end of the housing with a plug associated with one of the fibers being disposed in an alignment sleeve which in an opposite end thereof is adapted to receive a plug which terminates an optical fiber of another such connector to be assembled to this connector. Retaining facilities are disposed at an entrance to the other end of the housing to retain the sleeve in the housing and to guide a sleeve of another connector to cause another plug of this connector to be received in one end of the sleeve of the other connector. See U.S. Pat. No. 4,863,235 which issued Sep. 5, 1989 in the names of J. M. Anderson, et al.
The hereinbefore-described hermaphroditic connector is well suited to cables which include two optical fibers and which are to be terminated with biconic connector plugs. However, presently, there is much interest in the use of smaller ferrule connectors such as AT&T's ST.RTM. connector. Further, there are many instances when only single fiber optical cables are used. For the many applications of such a cable, there is a need for a single fiber hermaphroditic connector in which one terminated fiber cable may be connected directly to another such terminated fiber cable without the need for any intervening coupling device such as a coupling sleeve.
Seemingly, the prior art is devoid of a single optical fiber hermaphroditic ferrule connector. The sought-after single fiber hermaphroditic connector should be one in which non-metallic filamentary strength is maintained as such during the application of forces to the cable while not compromising the integrity of the strength members. Desirably, connection of the strength members to the connector is accomplished in a manner which causes the secured terminations to be enhanced when the cable is subjected to tensile forces.